1. Field of The Invention
The present invention relates to tools for sanding or grinding. More particularly, the present invention relates to a attachment for use with hand-held power tools for the purpose of grinding or sanding surfaces. More particularly still, the present invention relates to such an attachment and for a method of using it, with special applicability to elastic grinding belts.
2. Description of Related Art
As used in this document, the terms xe2x80x9cgrindingxe2x80x9d and xe2x80x9csandingxe2x80x9d are synonymous. Furthermore, a xe2x80x9cgrinding-belt,xe2x80x9d a xe2x80x9csanding-belt,xe2x80x9d a xe2x80x9cendless grinding belt,xe2x80x9d and an xe2x80x9cendless belt,xe2x80x9d are used interchangeably and refer to any closed-loop belt intended for sanding or grinding by means well known in the art. Finally, as used here, xe2x80x9ccylinderxe2x80x9d has its analytic geometry definition, which includes but is not limited to a cylinder in which the cross-section perpendicular to its axis is an ellipse.
Hand-held power tools used for drilling or grinding have long been popular and are in fact common household items. Building on this popularity, a number of devices directed at improving the sanding and grinding performances of these tools have been disclosed and introduced to the market. Typically, these devices are mechanically coupled to the power tool at the site where a standard attachment such as a drill-bit or sanding-wheel is otherwise placed. In spite of the advantages that these add-on devices may provide, they have not adequately addressed the problems associated with grinding or sanding surfaces intended to be non-flat. This is because these existing devices present either a flat or fixed-radius surface as a backing for the grind/sanding belt, a serious limitation for ornate work pieces incorporating curved portions. As a consequence portions of such complex and ornate work-pieces tend to be either over-worked or under-worked during the finishing process.
Nace (U.S. Pat. No. 4,551,951; 1985) discloses a detachable portable continuous-belt driving head for use in conjunction with an air-driven rotatable spindle. By wrapping a sanding belt around the work-piece, the Nace device can be used to sand or grind a significant portion of the circular contour of a cylindrical work-piece such as a pipe However, wrapping such a belt around an uninterrupted span of pipe requires that the belt be xe2x80x98seamed,xe2x80x99 that is that it has seam where it can be opened and then rejoined. In other words, before the Nace device can be used on a pipe, the ends of the grinding belt must be separated at the seam, the belt must be wrapped around the pipe, and the ends of the belt must be rejoined. This process is time consuming. Furthermore the use of seam-containing grinding belts can be hazardous, since they are vulnerable to operator error in connecting and disconnecting the belt that can lead to the belt flying off the rollers, causing injury or damage.
Kenig (U.S. Pat. No. 4,858,390; 1989) and Reiling et al. (U.S. Pat. No. 5,031,362; 1991) disclose similar endless-belt grinding attachments for use in conjunction with typical hand-held electric or pneumatic power-drills. Both of the Kenig and the Reiling et al. devices have a drive-pulley, driven by the output of a power tool, and an idler-pulley disposed at the end (distal to the drive pulley)of an arm member. In use, a grinding belt is mounted on these pulleys. Because the grinding belt so mounted conforms to a single longitudinal axis, these devices are limited to relatively small angles of contact when used with work-pieces having curved contours, such as pipes or toroidal shapes. Consequently, it is difficult to use the device of either Reiling et al. or Kenig to satisfactorily grind such curved surfaces.
Another invention using an endless grinding belt is that of Appleton (U.S. Pat. No. 4,578,906; 1986). The Appleton device is similar to those of Kenig and Reiling et al. in that it has two pulleys, one being a drive-pulley. These pulleys are mounted at the ends of a longitudinal arm-member. An endless grinding belt fits over the pulleys and is stretched to an essentially flat configuration, so that it presents a flat grinding surface to the work piece. A spring is mounted coaxially with arm-member and is used as a bias means for keeping the belt under tension and thus flat. The Appleton device has the same limitations as those described above. In addition, that fact that the Appleton device adds a motor for driving the drive pulley means that it is not just an attachment for a pre-existing power tool.
What is needed, therefore, is a an endless-belt device that can be used in conjunction with existing hand-held power grinding and drilling tools so as to enable those tools to more easily and effectively grind and sand work pieces that present curved surfaces. What is further needed is such an apparatus that can work the surface of complex, ornate shapes. What is further needed is a such an apparatus that can also provide proper backing for finish work on flat surfaces of a work-piece.
The present invention is an endless-belt grinder-attachment apparatus for any of the well-known hand-held power tools (e.g., power-drills or disc-grinders), the apparatus being configured so as to enable an operator of such tools to more proficiently grind or sand irregular surfaces, in particular curved surfaces. The apparatus is shaped so as to be affixable to the drive-shaft, axle, chuck, or spindle of the power tool with which it was to be used, thus permitting a drive-pulley contained within the body of the apparatus is driven by the underlying power tool. A key part of the apparatus of the present invention is a compound belt-support that is connected to, and extends from, the body of the apparatus. This belt-support has a primary-arm and a secondary-arm. An idler-pulley is disposed at each of the distal ends of the primary-arm and the secondary-arm, respectively. A grinding belt is fitted to the device in such a manner that, when the device is in operation, the belt runs around the drive-pulley and both of the idler-pulleys.
One of the arms of the belt-support is shaped in such a way that it can nestingly receive the other arm as the angle between the arms is reduced. This reception can be accomplished by one arm being made from three-sided channel stock having a generally U-shaped cross-section, thereby allowing the other arm to fit within the U. It is possible for both of the arms to be straight, both of the arms to be curved, or for one arm to be straight and the other curved. When an arm is curved, it may have a fixed radius of curvature (i.e., it may be arc-shaped) or it may have a varying radius of curvature, either decreasing or increasing as one moves from the arm""s proximal end toward to arm""s distal end.
If an arm is curved, one or more pulleysxe2x80x94in addition to the one at the distal endxe2x80x94are mounted along the arm""s convex side, so as to keep the belt from sliding on the convex side of the arm. Either or both of the two arms can be of fixed or adjustable length. The secondary arm is pivotably connected to the primary arm. One or both of the arms can have means for providing tension to the endless-belt. Tension may be effected with any suitable spring, elastomer (e.g., an element made of suitable rubber), or any equivalent, well-known means for providing tension.
The apparatus of the present invention is particularly well-suited for use with an elastic endless-belt (i.e., stretchablexe2x80x94as opposed to traditional endless-belts, which are merely flexible, such as is described in pending U.S. application Ser. No. 09/519,086, filed by the present inventors on Mar. 6, 2000. In those applications where an elastic belt is used, it may not be necessary to have separate tension-providing hardware on the device.
Located between the primary and secondary arms is a multifaceted support shelf, which adds greater flexibility to the operation of the apparatus of the present invention. When the two arms are collapsed into a single element, the support shelf is not deployed. When the arms are swung apart at their distal ends, the support shelf may or may not be deployed. Thus there are three qualitatively distinct configurations of the compound belt-support. The first, as stated, sees the secondary arm folded adjacent to the primary arm so that in effect a single arm is presented. In this configuration, the distance between the distal ends of the two arms, and consequently the angle between the two arms, are minimized. In a second configuration, the distal ends of the two arms are separated a sufficient allowing a work piece to enter the gap between the distal ends, while pressing against the belt. In this configuration, the work piece pushes the belt into the gap or sector between the two distal ends. In this mode of operation, the angle between the arms is allowed to freely vary depending on the size of the work piece and the distance the work piece is inserted into the gap (or sector) between the arms. The result is that the belt conforms to the general shape of the portion of the work piece inserted thereby effecting the sanding or grinding of curved and complex contours, in contrast with the limitation of the traditional devices that present only a flat or single-radius-of-curvature grinding surface to the work-piece.
In a third configuration, the support shelf, which is pivotably attached to the secondary arm, is unfolded from its folded position along the secondary arm, and its free end inserted into a receiving notch at the distal end of the primary arm, thus forming a triangular shape around which the moving belt conforms. This configuration enables the user to use any of the sides of the triangular shape for grinding. In addition, when one of the sides in this configuration is perpendicular to the longitudinal axis of the primary arm, a user can apply greater force to the work piece than is possible with the devices of the prior art.
By having two arm-elements, the present invention presents the user with more than one grinding surface with which to work. Additionally, with one arm able to move, the grinding surface can adapt to the surface of the work-piece being worked, with particular application to curved and complex shapes. For example, circular cylindrical members such as pipes can be worked upon by positioning the primary and secondary arms apart, yet with the support shelf remaining folded along the secondary arm. Because the belt spans the gap between the arms, and because in this configuration the support shelf does not support the belt, the belt can conform to the shape of a work piece forced against the belt. In this manner, a pipe may have up to one-half of its circumference sanded or ground concurrently by the present invention.
In another embodiment of the apparatus of the present invention, a vise insert may extend from the body, preferably in line with the longitudinal axis of the primary arm. In this manner the sander can be gripped in a vise, leaving the operator""s hands free to manipulate the work piece as it is pressed against the belt. Additionally, a stand may depend from the body of the apparatus, a stand adapted to stabilize the device while the device is used in conjunction with a typical power-drill that is laid on its side on a flat surface.
The apparatus of the present invention as described above should immediately lead one skilled in the art to various specific embodiments of the invention. The Preferred Embodiment of the invention is set out in detail below to give some definitiveness to the apparatus. However, there is no intention by so doing to limit the scope of the invention either by the Preferred Embodiment description or by the embodiments referenced in the Summary above.